Facts About Generators
GeneratorsDirectoryCompareRepairEnginesControllersPartsManufacturersGuides
Search models or part #
Home›Engines›Cummins/Onan QSX45-G

Cummins/Onan QSX45-G Engine

The Cummins/Onan QSX45-G is a 45 L 12-cylinder twin turbocharged engine rated at 1800 rpm. It powers generator sets from Cummins/Onan, including the QSK45.

Also known as: Cummins QSX45-G

45.0 L
Displacement
12
Cylinders
1800 rpm
Rated speed
On this pageSpecsGenerator setsFAQService intervalsTorque & specsFluidsProcedures

Engine specifications

Displacement45.0 L
Cylinders12
AspirationTwin turbocharged
Rated speed1800 rpm

Common problems

4
  • Overspeed OS
  • Low Oil Pressure LOP
  • High Engine Temperature Shutdown Fault 1
  • High Engine Temperature HET

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan QSX45-G.

Service intervals

2
ItemActionHoursMonthsNotes
Lubricating oilTest250 hr6 moFirst service — For high horsepower engines with Eliminator™ oil filter option: take oil samples every 250 hours and analyze per Cummins Engine Oil Recommendations Bulletin 3810340; repeat for at least three oil change intervals.
ELIMINATOR self cleaning filter coreOther1500 hrRequires servicing only every 1,500 hours. Saves up to 90% of lube system maintenance costs and increases productivity.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Service specifications

46
TypeItemValueUnitCondition
GapMagnetic pickup to ring gear tooth clearance0.71 to 1.07mm
OtherAnalog meter driver output current0 to 1mA
OtherDB9F-DB9M serial cable length (Part Number 4918418)1.83M
OtherDriver typeLow-Side (switched GND/Open)
OtherECM maximum operating current6.0 @ +24VDC (HPI-PT ECM); 7.2 @ +18VDC (HPI-TP ECM)A
OtherExtension DB9F to DB9M length (Part Number 3162851)30.48M
OtherFrequency adjust range±9Hz
OtherGovernor gain adjust range0.05 to 10.00
OtherINLINE™5 datalink adapter current requirement250mAat +8 VDC to +50 VDC
OtherMaximum sink current (driver ON)200mA
OtherMaximum supply current (lamp/relay driver supply)1.5A
OtherOpen circuit fault current (driver ON)< 2mA
OtherOutput accuracy< ±0.5% of Full Scale@ 100Ω meter load
OtherOutput resolution< 0.5% of Full Scale@ 100Ω meter load
OtherSpeed droop adjust range0 to 10%
OtherSwitch input maximum source current100mAwhen input is connected to signal GND return
OtherUSB cable length (Part Number 4918419)2M
OtherUSB cable length (Part Number 4918591)5M
ResistanceGCS ECM internal fixed resistor on remote gain/droop input2.87k Ohm
ResistanceMaximum driver impedance (driver ON)1Ω
ResistanceMaximum meter load impedance100Ω
ResistanceMaximum potentiometer resistance5KΩ± 5%
ResistanceMaximum supply impedance (lamp/relay driver supply)0.5Ω
ResistanceSuggested remote gain/droop potentiometer5k Ohmsuggested per Generator-Drive Control System Application Manual
TemperatureAmbient ECM heat sink operating temperature-40 to 60°C
TemperatureAmbient ECM housing operating temperature-40 to 70°C
TemperatureMaximum ECM heat sink surface temperature75°C@ 60°C ambient air temperature
TemperatureStorage temperature-55 to 80°C
TorqueKeyed connector thumbscrews0.79 - 0.90N m
TorqueMagnetic pickup jam nut34-47N-m
Voltage+0.2V speed bias signal5.0V ± 0.2VV
Voltage+2.5V speed bias signal5.0V ± 2.5VV
Voltage5VDC reference voltage+5VDC ± 2%VDC50mV p-p max ripple; 25mA max current
Voltage8VDC supply voltage+8VDC ± 5%VDC50mV p-p max ripple; 15mA max current
VoltageDriver voltage rating+24VDC nominal, +35VDC maximumVDC
VoltageECM operating voltage18 to 35VDCcontinuous; 10 VDC minimum during cranking
VoltageINLINE™5 datalink adapter supply voltage (maximum)+50VDCpower lamp fast flashing indicates greater than maximum
VoltageINLINE™5 datalink adapter supply voltage (minimum)+8VDCpower lamp slow flashing indicates less than minimum
VoltageLamp/Relay Driver Supply voltage+24VDC nominal, +35VDC maximumVDC
VoltageMagnetic pickup speed sensor output2.5 to 50VACunder any running condition (cranking or run speeds)
VoltageMaximum input voltage (analog inputs)5VDC
VoltageMinimum magnetic pickup speed signal input1.5 @ 200 rpm; 6.5 @ 1800 rpmVp-pat 200 rpm and 1800 rpm
VoltageNominal input voltage adjustment range (analog inputs)0 to 3.177VDC
VoltageRemote gain/droop analog input signal range0 to 3.177V
VoltageSwitch input switching threshold2.5VDC
VoltageSwitch input voltage+5VDC when ECM is in Sleep Mode or B+ (approx. 24VDC) when ECM is not in Sleep ModeVDC

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Recommended fluids

FluidGradeStandardAmbientCapacityNotes
Engine oilCummins Engine Oil Recommendations Bulletin 3810340Used to analyze oil samples for high horsepower engines with Eliminator™ oil filter option.
FuelB100 biodieselASTM D6751Must conform prior to blending; revised to include a cold soak test; stability requirement still in effect.
FuelB20 biodiesel blendASTM D7467Applies to biodiesel blends B6–B20; includes oxidation stability requirement; replaces Cummins' previous EMA B20 specification requirement. Must be purchased from a BQ9000 Certified Marketer; B100 must be sourced from a BQ9000 Accredited Producer.
FuelB5 biodieselAll Cummins automotive and industrial engines are compatible with B5 biodiesel.
Fuelbiodiesel (Europe)EN 14214Published by CEN, European Committee for Standardization. Equivalent biodiesel specifications required internationally.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Procedures

5
Magnetic Pickup Adjustment adjustment

⚠ Jam nut over-torque will damage the magnetic pickup.

Tools: feeler gauge, torque wrench

  1. Ensure a ring gear tooth is centered under the magnetic pickup hole. Rotate flywheel if necessary.
  2. Screw the magnetic pickup in until it contacts the targeted gear tooth. Do not use excessive pressure.
  3. Back the magnetic pickup out (counterclockwise) 1/2 to 3/4 turn.
  4. If a feeler gauge can be inserted between the magnetic pickup and the flywheel ring gear tooth, back the magnetic pickup out 0.71 to 1.07 mm [0.028 to 0.042 in.] from the gear tooth.
  5. Tighten the jam nut on the flywheel housing. While holding the magnetic pickup, torque the jam nut to 34-47 N-m [25-35 ft-lb].
Connect the INLINE™5 Datalink Adapter to a Personal Computer installation

⚠ A fully populated USB cable, Part Number 4918419, or DB9F-DB9M serial cable, Part Number 4918418, must be used.

  1. Connect the DB9F-DB9M serial cable, Part Number 4918418, or USB cable, Part Number 4918419, to the computer.
  2. Connect the other end of that cable to the INLINE™5 datalink adapter, Part Number 3165033.
  3. Supply +8 VDC to +50 VDC at 250mA through the OEM connector or a separate power source.
  4. Connect the appropriate datalink cable to the INLINE™5 datalink adapter, Part Number 3165033.
  5. Connect the other end of the datalink cable to the vehicle cab or engine compartment datalink connector.
  6. Launch the electronic service tool application software.
Keyed Connector Backshell Assembly installation

Tools: Wire Strippers, Standard Screwdriver, Terminal Crimp Tool

  1. Position the connector grommet seal on the backside of the connector.
  2. Strip 4.3 to 5.1 millimeters (0.17 to 0.20 inches) of insulation from the ends of the wire harness conductors.
  3. Using the appropriate terminal crimping apparatus, crimp the connector terminals onto the stripped, bare ends of the wire harness conductors. Use a crimp tool with frame style M22520/2-01 per MIL-C-22
  4. Once all conductors to be used are crimped onto connector terminals, insert each terminal into the correct cavity of the connector.
  5. The grommet seal must have a sealing plug inserted in the unpopulated cavity positions.
  6. Ensure that all terminals are properly seated into each of the connector cavities.
  7. Place the connector into one half of the keyed backshell, laying the harness bundle as shown.
  8. Place the strain relief clamp over the harness bundle and attach it to the backshell half using the two strain relief clamp screws provided.
  9. Place the two thumbscrews into the proper locations of the backshell half.
  10. Place the second half of the backshell in place, fitting it to the first half, and fasten the two backshell halves together using the two backshell fastening screws provided.
Oil sampling for high horsepower engines with Eliminator™ oil filter option maintenance
  1. Take oil samples every 250 hours of operation.
  2. Analyze samples according to Cummins Engine Oil Recommendations Bulletin 3810340.
  3. Repeat for at least three oil change intervals to ensure consistent oil behavior.
Switching from petrodiesel to B20 on used engines maintenance

⚠ B20 has a solvent nature and may clean the vehicle fuel tank and lines.

  1. Install new fuel filters when switching to B20.
  2. Replace fuel filters at half the standard interval for the next two fuel filter changes.
  3. After the initial period, revert to intervals specified in the O & M manual.
  4. For EPA 2007 on-highway midrange engines, sample oil for the first 6 months to monitor fuel dilution.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Common questions

What is the displacement of the Cummins/Onan QSX45-G?

The Cummins/Onan QSX45-G has a displacement of 45.0 liters with 12 cylinders.

Which generators use the Cummins/Onan QSX45-G engine?

The Cummins/Onan QSX45-G powers 1 generator set(s), including Cummins/Onan QSK45.

What is a common problem with the Cummins/Onan QSX45-G engine?

A commonly reported issue on generators using the Cummins/Onan QSX45-G is: Overspeed.